In today's electronic equipment, electrical interconnection is often provided by a plurality of rows of connectors mounted to a backplane or mother board interconnected to respective corresponding mating electrical connectors mounted to a plurality of daughter cards. Generally the connectors extend along the full length of the daughter card and include a highly dense array of contact members. In bringing such connectors into mating engagement it is necessary that the corresponding terminals engage and mate in associated pairs. Typically the daughter cards are mounted in card guides to aid in proper alignment of the connectors. For high density connectors having many small contact members, however, precise alignment requires more than just the card guide and frame members. The connectors, therefore, must also be provided with aligning means that complete the alignment prior to mating engagement of the terminal members. Furthermore, it is also desirable that keying means be provided to allow mating of connectors intended to be mated and disallowing mating of connectors not intended to mate.
In interconnecting the mother board or backplane to the daughter boards, it is often necessary to transmit both power as well as signal lines between the boards. Typically this has been accomplished by having one or more power connector units and one or more signal connector units positioned along the mating interface. In order to meet the demands of the industry to minimize the size of electronic equipment and provide for a maximum number of electrical interconnections, it is desirable to provide highly dense connectors that require a minimum amount of space on the respective boards.
It is further desirable to provide an array of modular connector units whereby the location of the power and signal lines can be readily located at the desired intervals position in each connector array by inserting the appropriate module.
Owing to the current being carried by the power portion of the interconnecting systems, certain safety requirements must also be met to prevent accidental touching of the power contacts by a human finger. In one commercially used safety test, a blunt ended probe having a diameter not less than 0.25 inches is used to test the safety of the contact array. To pass the test, the probe must be prevented from engaging any power contacts of the array.
Furthermore, it is also desirable to include means for aligning the corresponding connectors prior to engagement of the complementary contact members therein, to prevent damage to the corresponding mating power or signal contact members.
It is further desirable to have means for keying the corresponding mother board and daughter board connectors to assure accurate interconnection of the desired power and signal lines.
While it is known to provide aligning and keying features for electrical connectors, typically these features are added at the ends of the mating connectors thereby requiring additional space in the array of ganged connector modules. U.S. Pat. No. 4,726,791 discloses one such keying system for connectors comprising hexagonally shaped key members disposed in key-receiving passageways adjacent the ends of the contact arrays in the plug and receptacle sections of the connector. U.S. patent Ser. No. 07/252,220 discloses another type of aligning and keying system for mounting connectors in a framework having both axial and angular centers. The connector is used to interconnect a mother board to a daughter board. Alignment pins and key members are located along the exterior edges of the connector housing and intermediate adjacent connectors in a row of connectors.
It is desirable to provide for keying or polarization of the plurality of ganged connectors while minimizing the space required on a board.